Agricultural applications of PAM are well known in the prior art. Specifically, PAM has been used in agricultural applications to prevent soil erosion in irrigation ditches and reduce sediment in irrigation water. PAM is a long-chain synthetic polymer that acts as a strengthening agent, binding soil particles together. The bound soil particles become relatively large aggregates and are too heavy to remain suspended in the water. Because the soil aggregates are heavy, they fall to the bottom of the irrigation ditch and settle into the cracks in the ditch bottoms rather than eroding out of the irrigation ditch.
Erosion prevention is desired in agriculture because the topsoil is the most fertile area for crops to grow. When crops are irrigated without adding PAM to the system, topsoil erodes as the irrigation water passes over the soil. The soil particles are moved by the force of the water and are deposited at the end of the irrigation ditch. The erosion process is slow, however, the topsoil is gradually removed, and the fields become less productive.
Another problem associated with erosion is plant water stress. As the growing season progresses and crops are regularly irrigated, the irrigation ditches can become narrow, deep-cut channels due to erosion. Depending on how deep the channels become, the irrigation water may be applied below the most active portion of the root zone of the plant. When this occurs, the crops experience water stress. To reduce the water stress, the irrigation water must be moved up in the soil profile, which requires a constant water source and is costly and inefficient.
In addition to erosion control, PAM can increase the intake rate of some soils. Without PAK soil particles come into suspension in the irrigation water. The small soil particles find their way into the larger pore spaces on the bottom of the irrigation ditch and form a seal on the bottom of the irrigation ditch with finely packed small soil particles. Thus, the infiltration rate of the soil is reduced. However, when PAM is added to the irrigation water, its binding particles increase the infiltration rate by maintaining the soil structure. The aggregates formed by the PAM contain microscopic pores through which water can pass. These aggregates fall onto the bottom of the ditches and make it easier for the water to pass through the soil than when the finely packed small soil particles coat the ditch. The increased intake rate of the soil helps with rut prevention caused by center pivot irrigation system tires.
Prior use of PAM has been disclosed in U.S. Pat. No. 6,749,748 (Macpherson et al.), U.S. Pat. No. 6,669,752 (Arnold et al.), U.S. Pat. No. 6,395,051 (Arnold et al.), U.S. Pat. No. 6,000,625 (Cole), U.S. Pat. No. 5,749,672 (Chamberlain et al.), U.S. Pat. No. 5,450,985 (Meuleman), U.S. Pat. No. 4,820,424 (Field et al.), U.S. Pat. No. 3,860,526 (Corbett), U.S. Pat. No. 3,839,202 (Roy), and U.S. Pat. No. 3,435,618 (Katzer). However, each of these disclosures suffers from one or more of the following disadvantages. First, the PAM forms previously disclosed are not pure active ingredient. The prior art PAM forms include fixing agents that account for the majority of the mass of the PAM form. The fixing agents are present in the prior art for various reasons including, but not limbed to, aiding the release of PAM molecules and aiding in binding the PAM into a solid form. Second, the PAM forms previously disclosed must be placed in a turbulent flow stream in order to dissolve. If the PAM forms are not placed in turbulent flow conditions, they will not dissolve quickly enough to provide sufficient molecules to prevent erosion. Third, at least some the PAM forms previously disclosed are powder tablets. The powder tablets break easily and the powder blows away. Fourth, at least some of the prior art PAM forms require high molecular weight PAM. What is needed is a PAM delivery product that dissolves relatively easily, requires no fixing agents, and does not easily break apart and blow away.